The overall objectives of this project are to elucidate the mineralization mechanism in the mollescan bivalve hinge ligament, to formulate unifying processes in invertebrate and vertebrate mineralizing systems, and to determine why some tissues mineralize and other do not in order to understand those factors which contribute to pathological mineralization. In the coming year ultrastructural studies on the hinge ligament-isthmus epithelium junction will be initiated on small specimens of Aequipectin irradians, in order to elucidate structural intermediates in the formation of the ligament. The remainder of the experimental work will be principally in protein chemistry and will include: 1. Amino acid analysis and comparison of the protein phase in the calcified and noncalcified protions of the hinge ligaments of Aequipecten irradians and Placeopecten magellanicus. Isolation and analysis of the fiber network component from the noncalcified area of these ligaments. 3. Attempts to isolate and characterize the intensly osmiophillic elements of the crystal sheaths in calcified ligaments. 4. Initiation of amino acid sequence studies on the bulk hinge ligament elastomes which is as high as 66% glycine in some species.